This project is concerned with the investigation of the molecular biology of human cytomegaloviruses (human CMV) in order to elucidate the mechanisms of viral pathogenesis and latency and the possible basis of viral oncogenesis. The approach is based on our recent developmental work and can be categorized as follows: (a) physical and genetic analysis of viral DNA by restriction endonucleases (EcoR1, Hinb III and Hae); (b) a study of the mechanism of viral DNA replication with the use of inhibitors of macromolecular synthesis and the detection of the initiation site(s) and polarity of CMV DNA replication by electron microscopy and restriction enzyme analysis. The isolation and characterization of virus-induced DNA polymerase(s) by column chromatography and synthesis of CMV DNA in isolated nuclei is outlined in related work; (c) a study of the regulation of gene expression in CMV-infected permissive cells, in non-productive cells and in virus- transformed cells approached by nucleic acid hybridization techniques and immunological analyses; (d) the genetic relatedness between CMV and other herpes group viruses, i.e., herpes simplex type 1 and 2, Epstein- Barr virus, varicella-zoster, Herpesvirus saimiri, Herpesvirus ateles by DNA-DNA reassociation kinetics analysis and S1 enzyme differential digestion; (e) the classification of strains of human CMV by DNA fragment pattern analyses, by DNA-DNA reassociation kinetics analysis and heteroduplex formation as well as by immunologic relatedness; and (f) localization of the viral genome and viral antigens in human tissue and determination of susceptible cell types and organs by in situ H3 cRNA-DNA cytohybridization and anti C'-3 immunofluorescence (ACIF) techniques to explore the natural state of CMV, both latent and replicating, in man. This approach should provide the necessary first step for an understanding of the phenomena of latency and reactivation of human CMV, increasingly recognized as an important pathogen. This little understood pathogen of man may also have an yet little explored oncogenic potential.